If i undestand you correctly you have page1 and page2 and you dont want your users to access page2 without accessing page1. if that is the case you have to use Sessions to do this.

in page1 you can create a session variable that will tell you that it has been accessed and clear it when the second page is closed. And in the second page check if the session is null if its null send the user to page1

like this

Session[Accesed] = "Accessed";

First in your page2 page load event , check if the session created in page1 session if its Null like this